1. Field of the Invention
The present invention relates to a semiconductor device comprising at least a semiconductor film accompanying lattice distortion therein, and to a method for manufacturing the same.
2. Description of the Prior Art
Methods for fabricating polycrystalline semiconductor films to use in polycrystalline semiconductor devices include (1) depositing films in the temperature range of from 550.degree. to 900.degree. C. using low pressure CVD (chemical vapor deposition), (2) thermally crystallizing semiconductor films having deposited by low pressure CVD, by annealing the films in the temperature range of from 550.degree. to 650.degree. C. for a duration of from several to several tens of hours, and (3) thermally crystallizing semiconductor films having deposited by plasma-enhanced CVD, by annealing the films in the temperature range of from 550.degree. to 650.degree. C. for a duration of from several to several tens of hours.
However, in depositing a non-single crystal semiconductor film, a reduced pressure CVD method fails to deposit uniformly the film over a large area on a substrate, and a plasma CVD method takes too long a time to deposit the film to a sufficient thickness.
There is also known a method of fabricating thin-film transistors using an amorphous silicon (a-Si) film having deposited by sputtering in the presence of hydrogen, however, the electric characteristics of the resulting thin film are so poor as to yield, e.g., an electron mobility of 0.1 cm.sup.2 /Vsec or even lower.
If a non-single crystal semiconductor film is deposited by a sputtering method under an atmosphere free from hydrogen, on the other hand, the resulting film suffers segregation of silicon atoms. Furthermore, it is known that such a film would not undergo thermal crystallization at 700.degree. C. or at any temperature below 700.degree. C., due to the incorporation of impurities such as argon and oxygen atoms or to the lack of hydrogen, or due to both.